1. Technical Field
The present disclosure relates to reducing emission of particulate matter from a direct-injection gasoline engine.
2. Background Art
It has been found that particulate matter is emitted from gasoline direct-injection engines during the first 500 seconds of the Federal Test Procedure, i.e., when the engine is not yet warmed up. Particulate matter is presumed to be formed by fuel directly contacting surfaces of the combustion chamber, and in particular the piston tops (especially if they are oil cooled) as they warm up more slowly than the cylinder walls and the cylinder head.